Method of making springs



Nov. 7, 1961 BLLERMONT METHOD OF MAKING SPRINGS Original Filed May 28,1949 5 Sheets-Sheet 1 BASIL LERMONT,

B. LERMONT METHOD OF MAKING SPRINGS Nov. 7, 1961 9 4 9 l 8 2 V.- a M d el i F l a n i g i r O BASIL LERMONT,

film, 5mm Q ALI-4M Nov. 7, 1961 B. LERMONT METHOD OF MAKING SPRINGSOriginal Filed May 28, 1949 5 SheetsSheet 3 BASIL LERMONT, a, m dlv-ANov. 7, 1961 B. LERMONT METHOD OF MAKING SPRINGS Original Filed May 28,1949 5 Sheets-Sheet 4 FIG.|8.

BASIL LERMONT,

FIGJQ.

United States Patent METHOD OF MAKING SPRINGS Basil Lerinont, New York,N.Y., assignor, by mesne assignments, to American Machine and Metals,Inc.,

New York, N.Y., a corporation of Delaware Application Aug. 22, 1952,Ser. No. 305,899, now Patent No. 2,801,669, dated Aug. 6, '1957, whichis a division of application Ser. No. 95,956, May 28, 1949, now PatentNo. 2,609,192, dated Sept. 2, 1952. Divided and this application Nov.21, 1956, Ser. No. 623,683

4Claims. (Cl. 29-173) This invention relates to certain improvements inmethods for manufacturing coil springs, and particularly to methods forproducing springs which are characterized by varying resistance tounwinding and/or equal resistance to unwinding or straightening(constant tension) at all zones along the length of the springs.

This application is a division of my application Serial No. 305,899,filed August 22, 1952, and issued August 6, 1957, as Patent No.2,801,669, which, in turn, is a division of my application Serial No.95,956, filed May 28, 1949, and issued September 2, 1952, as Patent No.2,609,192. Application Serial No. 95,956, supra, is acontinuation-impart of my now abandoned application Serial No. 747,189,filed May 1947.

It has been usual heretofore in the production of spiral springs andother types of springs to twist or wind a strip of metal on a mandrel orcylindrical form to bend the spring into a desired shape. This coiledstrip of metal is then tempered or otherwise treated to render itresilient and to fix or set its normal shape. Due to the method offormation of such spiral springs, each increment of the spring assumes aslightly diiferent radius of curvature in conformance with its initialstate of winding with the result that the force required to straightenany given increment differs from the force required to straighten allthe other increments of the spring.

it has also been usual heretofore in spring forming machines, to bendwire stock on a constant radius and to employ a skew or pitch member tocontinuously deflect the bent material axially into a helix, rather thanto allow the material to coil tightly upon itself into a spiral with itsconvolutions disposed in a substantially common radial plane.

It has been further suggested heretofore that coils of metal tinselstrip and other articles can be formed by drawing a strip of metal overa sharp edge to bend the strip and cause it to coil into generallyhelical form. Such coiled tinsel strips are commonly used in theproduction of scouring pads which are used for cleaning kitchen utensilsand the like. It appears that the tendency of the strip to form a helixrather than a spiral arises because the strip is maintained undertension while it is drawn over the forming head, thereby producing aflow of the metal of unequal magnitude along the strip. It has also beensuggested that circular hoops for wagon tires or the like could beproduced by passing a strip of metal between a pair of rollers and thendeflecting or bending the strip by pushing it against the periphery of athird roller or abutment member so that the strip tends to form a circleor annular ring.

None of these prior devices has been used to produce a self-winding coilspring, each increment of which is purposely bent on the same radius ofcurvature and/ or on a predetermined varying radius of curvature, andwhich is essentially constant in its resistance to straightening orunwinding throughout its entire length, so that the spring acts much inthe manner of a counterweight when suitably assembled with a support ormounting, rather than as a rnernberof variable tension throughout itslength.

ice

In accordance with the present invention, such a constant tensionspring, that is, a spring every increment of which requires an equalforce to straighten it, is produced by drawing or passing a strip ofmetal between two forming elements to bend the strip partially so thatevery increment of the spring is bent on an equal radius and so theconvex surface portion is stretched while the concave surface portioneither is unstretched or actually is compressed slightly. Due to theuniform deformation of the strip, every increment of it is stressedequally and it will tend to coil into one or more convolutions each ofwhich has the same radius of curvature when unrestrained.

When such a spring is mounted so that it can turn freely and a force isexerted on one end of the spring tending to unwind it, it acts Very muchlike a counterweight for the reason that any tension applied to thespring will tend to straighten that portion which is tangent to theouter surface of the coiled portion of the spring. Inasmuch as everyincrement of the spring is equally stressed and bent, the force requiredto straighten any given portion of the spring is exactly the same as theforce required to straighten any other portion of the spring. Therefore,the resistance to straightening or drawing out of the spring is notcumulative. That is to say, a force strong enough to straighten orunwind one end of the spring will, if continuously applied, completelystraighten out or unwind the entire spring, assuming, of course, thatthe convolutions or coils of the spring are all allowed toassume theirnormal state. Thus, a spring which has been formed with a predeterminedconstant radius of curvature and is equally stressed throughout, ifallowed to form itself into a plurality of independent coils orconvolutions in which each coil is not obstructed or distorted bycontact with other convolutions, will have the above-mentioned constanttension characteristics. On the other hand, if the spring is allowed tocoil upon itself, that is, to coil into a tightly wound spiral, theconstant tension characteristics are modified by the following factors.It is evident that no two of the convolutions, even if equally bent, canoccupy the same space. As a result, one or both of the convolutions mustflex to different curvatures from their normal constant radius ofcurvature. Therefore, when a straightening force is exerted on the freeend of the spring, a greater or lesser straightening will result as thespring unwinds, and the force required to straighten the spring willvary accordingly.

Also, in the case of a spirally coiled but constant radius spring, theradius or moment arm of the force acting on the spring becomes less andless as the spring is unwound, thereby requiring an increasing force tounwind the spring.

To overcome the eifects of the varying moment arm and the partialstraightening of the spring because of space limitations, in spirallycoiled springs, the spring can be modified either by varying theresistance to straightening throughout the length of the spring, forexample, by varying its radius of curvature throughout so that the outerend portion of the spring normally tends to curve, when in repose, on ashorter radius than its inner end portion, or by tapering or perforatingthe spring throughout its length. These variations in the spring shouldbe such as to just offset or compensate for the change in deflection ofthe spring and the change in the length of the moment arm of the springas it coils and uncoils.

The forming devices disclosed herein are capable of producing springsformed with any desired constant radius or with any desired varyingradius. The radius of curvature of the spring can be modified byadjusting the sharpness or abruptness of the bending of the springmaterial, and in order to accomplish this function, different anvilblocks or die members, having difierent radii of curvature may be used,or an anvil member of a fixed curvature but having a cooperatingadjustable retaining or holddown member for altering the width of thegap between the two members to correspondingly vary the radius ofbending of the strip, may be provided.

The manner in which the strip is passed through the gap between the diemembers may be varied. Preferably, the strip is drawn over the diemember without any tension being exerted on the trailing end of thestrip. If the strip is of sutficiently heavy gauge, it may be forcedover the anvil or die member by means of suitable feed rollers so thatthe strip is not maintained under tension during its forming operation.

The principal object of the present invention is to provide springshaving constant and/or variable tension characteristics, and methods forproducing such springs.

For a better understanding of the present invention, reference may behad to the accompanying drawings, in which:

FIG. 1 is a diagrammatic perspective view of a typical form of apparatusfor making springs of the type embodying the present invent-ion;

FIG. 2 is a view in section through the die or forming elements taken online 2-2 of FIG. 1;

FIGS. 3 is a perspective view of a coil spring of a character which canbe formed by the apparatus illustrated in FIGS. 1 and 2;

FIG. 4 is a diagrammatic illustration of a modified form ofspring-forming device involving the use of feed rollers for pushing thestrip through the die gap;

FIG. 5 is a diagrammatic view illustrating the relationship between apiece of spring material and a pair of dies, such as shown in FIG. 4,during the bending operation on the spring material to form it into acoil spring;

FIG. 6 is a perspective view of a constant tension spring which can bemade by the apparatus of FIGS. 4 and 5, the spring, however, being shownassembled with a support;

FIG. 7 is a perspective view of a spring in which all increments thereofare bent upon a given constant radius;

FIG. 8 is an elevational view of a spring of the type shown in FIG. 7,wherein portions of the spring are wound in reverse directions;

FIG. 9 is a diagrammatic view illustrating one practical application ofthe constant tension spring shown in FIG. 8;

FIG. 10 is a perspective view of a spring which is perforated to modifyits tension characteristics to compensate for variations in the momentarm and inability of a plurality of convolutions of the spring to occupythe same space;

FIG. 11 is a perspective view illustrating another practical applicationof the present spring, wherein the spring is supported on a rotatableshaft or arbor for producing a constant tension eflect;

FIG. 12 is a perspective view of a modified form of mounting for aspring having constant tension characteristics;

FIG. 13 is a perspective view illustrating another form of springassembly having constant tension characteristics;

FIG. 14 is a diagrammatic perspective view of a modified form ofapparatus including a control cam for automatically making constanttension springs having a uniformly varying radius of curvature;

FIG. '15 is an elevational view of another spring assembly including aspring, which may be formed on a constant radius by the apparatus shownin FIG. 4 or formed on a progressively varying radius by the apparatusshown in FIG. 14, adapted to serve as a counterbalance for a window sash(not shown);

FIG. 16 is an elevational view of a modified cam adapted for use in theapparatus shown in FIG. 14 to automatically form a spring having theopposite end portions thereof bent upon different constant radii and anintermediate portion bent upon a varying radius;

FIG. 17 is a schematic elevational view of a spring that can be producedby substituting the cam shown in FIG. 16 for the cam presently shown inFIG. 14;

FIG. 18 is a diagrammatic view, partly in cross-section, of another formof automatic machine for bending spring material upon any desired radiusof curvature, either constant and/or progressively increasing ordecreasing;

FIG. 19 is a detail sectional view taken on the line 19-19 of FIG. 18;

FIG. 20 is a plan view of the automatic machine shown in FIG. 18;

FIG. 21 is a detail sectional view taken on the line 2121 of FIG. 20;

FIG. 22 is a diagrammatic view illustrating one form of drivingmechanism for the machine shown in FIGS. 18 to 21;

FIG. 23 is a diagrammatic view illustrating a cam and other elementsassociated with an electrical circuit for automatically controlling themachine;

FIG. 24 illustrates a modified form of cam adapted to be substituted inthe control mechanism shown in FIG. 23 to form a spring having the endportions thereof formed on uniformly varying curvature and theintermediate portion thereof bent upon a constant radius; and

FIG. 25 is a schematic view of a coil spring that can be formed underthe control of the cam shown in FIG. 24.

The apparatus described hereinafter is typical of the many differentforms of devices by means of which springs of the type embodying theinvention can be produced and, therefore, should be considered asillustrative only.

Referring now to FIG. 1, a simple form of apparatus for forming springsof the type embodying the present invention may consist of a base member10 which may take the form of a block of reinforced concrete or a metalbeam having at one end an upstanding lug 11 to which the cylinder 12 ofa hydraulic jack is fixed by means of a pivot pin 13 extending throughthe clevis 14 at the end of the cylinder and through the lug 11.

The piston rod 15 of the cylinder is provided with a pair of pivotallyconnected gripping jaws 16 and 17 having suitable hand screws 18 and 19therein for forcing the blocks 16 and 17 together to grip the end of anelongated piece or sheet of flexible metal 20, from which a spring is tobe formed. The sheet 20 can be of any of the conventional types ofspring steel or an alloy, such as a beryllium-copper alloy. It may evenbe formed of stainless steel which has been found to have excellentspring properties when treated in accordance with the present invention.

The opposite end of the base member 10 is provided with an anvil blockor lower die member 22, which, as best shown in FIG. 2, may consist of abar of metal having parallel opposite sides 22 and 22 a lower side 22which is perpendicular to the sides 22* and 22 and an upper side 22which is inclined at an acute angle to the side 22*. The junction of thesides 22 and 22 is curved to form a generally arcuate or rounded convexsurface 22 of a radius of curvature which is dependent upon the desiredradius of curvature of the spring being formed,

a as will appear more fully hereinafter.

The strip 20 passes over the rounded surface 22 and is bent intoconformity with the shape of this surface by means of a second die blockor hold-down member 23. This hold-down member preferably is providedwith a recessed undersurfaee having a concave surface portion 23 whichis concentric with the surface 22 On opposite sides of the concavesurface 23 are right angularly related surfaces 23 and 23 which engagethe outer surface of the strip 20 and aid in bending it around thesurface 22e. As will be obvious from FIG. 2, the surfaces 22*, 22 22 2323 and 23 cooperate to define an angular or generally L-shaped gaptherebetween. The shape of the upper and lower die blocks 23, and 22,respectively, aside from the relationship of the surfaces 22 22 and 22and the surfaces 23*, 23 and 23, is unimportant.

The two blocks 22 and 23 are retained in their desired relationship bymeans of the stud bolts 24 and 25 at opposite ends of the die members 22and 23. The lower end of the stud bolt 24 is anchored in a lug 26 on theend of the die block 22 while the upper end passes through an opening inthe upper member 23 to receive a nut 27 for clamping the two die memberstogether. The stud bolt 25 is similarly mounted at the opposite end ofthe die block 22 and is provided with a nut 28 for holding the diemembers 22 and 23 in contact with the sheet 20. The bolts 25 extend in aplane AA (FIG. 2) coinciding with a radius passing through about themidpoint of the arc defining the rounded edge 22 In operation, thepiston rod 15 is advanced by admitting fluid into the cylinder 12through the conduit 3% until the gripping plates 16 and 17 are closelyadjacent to the die block 2-2 and the end of the sheet of metal 20 isthreaded through the gap G between the die blocks 22 and 23 while theyare spread apart a greater distance than the thickness of the sheet. Theend of the sheet is then clamped between the gripping plates 16 and 17,and the upper die block member '23 is tightened down by adjustment ofthe nuts 27 and 28 until the portion of the sheet 20 between the dieblocks is bent into conformity with the curvature of the forming surface22". Pressure is then applied to the cylinder 12 through the conduit 30to draw the sheet 20 over the curved forming edge 22?, thereby bendingthe sheet sharply and stretching the outer portion of the sheet. Suchstretching imparts a permanent set to the metal, and when the freetrailing edge of the sheet finally passes by the forming edge 22 thesheet will coil tightly upon itself with its convolutions disposed in asubstantially common radial plane to form the spring 8 shown in FIG. 3.The drawing action of the cylinder, while having some tendency tostraighten the sheet 20, has been found to act equally throughout thelength of the sheet so that while its radius of curvature R isconsiderably greater than the radius of curvature of the forming surface22 the amount of curvature throughout the length of the bent portion ofthe sheet is exactly the same for any increment thereof. The end 20' ofthe strip 20 which was clamped between the jaws "16 and 17 remainsstraight, as shown, and may be provided with an opening 20" tofacilitate attachment thereof to any object.

Springs of still greater radius of curvature can be produced byloosening the nuts 27 and 28 separately or simultaneously to permit dieblock 23 to retract somewhat to increase the width of the gap G so thatthe sheet 20 is not bent as much as when the block 23 is held downtightly against the upper surface of the sheet. The nuts 27 and 28 canobviously be manually adjusted while the sheet 20 is stationary, or inmotion. Also, interchangeable die blocks may be used in which the radiiof curvature of the surfaces 22 and 23 are greater or lesser in order toform springs of different curvatures.

In order to offset any tendency of the cylinder 12 and the piston 15 tostraighten the strip or sheet, springs may be produced by forcing,instead of pulling, the strip between die blocks similar to thosedescribed above. As shown in FIG. 4, the die blocks 35 and 36 thereinmay be similar to the die blocks 22 and 23. The lower die block 35 issupported in a suitable frame, not shown, which also supports a pair ofdriven feed rollers 37 and 38.

The elongated piece or sheet of metal 39 is gripped between the rollers37 and 38, which are positively driven in opposite directions by meansnot shown, to force the sheet 39 between the die block members 35 and 36so that the sheet will be bent as described above and will form a tightcoil at the discharge end of the die blocks 35 and 36.

In forming coil springs with the apparatus shown in either FIGS. 2 or 4,it is generally preferable to have the die members 23 and 36 spaced fromthe die members 22 and 35, respectively, a distance somewhat greaterthan the thickness of the material which is passed therebetween. Thewidth of the space or gap between the dies 35 and 36, as indicated bythe dimension G in FIG. 5, will vary with the character and thickness Tof the spring material. The draw radius R, or radius of curvature of therounded edge 2 2 of the die member 22 and the corresponding edge of thedie member 35, will also vary with the character and thickness of thespring material. Assuming that the spacing or gap G between the diemembers is not adjusted during a spring-forming operation, then theradius R will be constant for any increment a, a", or a of the springmaterial passed between the die members. The bend radius, of course, canbe varied by increasing or decreasing the dimension of the gap G so thatcoils having any predetermined constant or varying radius of curvaturecan be produced, as desired.

The radius of curvature R will also be predetermined in the light ofpractical consideration by proper design of the die members with dueconsideration being given to the kind of material employed and itsdimensions, as will appear hereinbelow.

For most purposes, resilient, cold rolled strip material is preferred.By way of operative examples, the springs may be made of high carbonstrip steel, S.A.E. No. 1095 having a width of /2 and a thickness of A(.016). When this particular material is used, it is preferable to use adie block in which the draw radius R is or .0625", and the gap G betweenthe die blocks is .038". Each resulting coil will then tend to assume anormal diameter of or 1.375", with each successive increment of thespring bent upon a constant radius R. Such a spring has been found torequire a constant force of only 66 ounces, or 4 lbs. and 2 ounces toeffect unwinding thereof regardless of the number of convolutions thatare unwound.

As a further operative example of the invention, the springs may beformed of a strip of stainless steel having a thickness of .011" and awidth of 1". In coiling such material, the draw radius R on the dieblock is preferably or .156" and the gap G between the die blocks ispreferably .016". The resulting coils will then have a normal diameterof 1 with each increment bent upon a constant radius of curvature R. Theload tension capacity of such spring is 60 ounces, or 3 and /4 lb.

The cross-sectional shape of the material from which the spring isformed can be varied substantially. Thus, the spring can be formed ofwire or the like, of circular, square or triangular cross-section orfrom thin strip material and the like of any suitable width.

The spring material 39 may be fed from a supply roll (not shown) orconsist of strips of predetermined length, which may be bent upon aconstant radius throughout to form a coil spring S as illustrated inFIG. 7. On the other hand, a predetermined length of the material 39 maybe bent upon a constant radius and a portion left unbent to provide aspring S having an end 39 which is in a straight condition, as shown inFIG. 6. In the event of the latter, the die blocks 35 and 36 areseparated when the desired portion of the spring has been bent, so thatthe end portion 39 of the spring material remains unbent or straight.When the spring material 39 is fed from a supply roll, completed springscan be severed by conventional cut-oft means (not shown).

In FIG. 6, the spring S is operatively assembled with supporting meansshown in dot-and-dash lines and comprising a drum 39 (to which the innerend of said spring can be secured, if desired) supported upon a shaft 39rotatably mounted in a bracket 39.

The spring shown in FIG. 7 has an inner end W and an outer end X. Thelatter end may be unwound and then rewound, as illustrated in FIG. 8, toform two coil portions S and S In such case, the pressure at the zone ofcontact of the coils, indicated by the letter Y, will be substantiallyconstant irrespective of the number of convolutions comprising therespective coil portions S and S As illustrated, each coil portion S andS comprises two convolutions, the outermost of which are inherentlyurged toward each other by a force efiective at Y. The force at Y wouldbe substantially the same if one of the coil portions had only oneconvolution and the other had three.

FIG. 9 diagrammatically illustrates one practical application of thetype of coil spring shown in FIGS. 7 and 8. Here, the end X of thespring is wound around a roller M rotatably mounted upon a pin P carriedbetween the arms of a yoke A. The opposite end W of the spring is woundaround a similar roller M rotatably mounted upon a pin P carried byanother yoke A. The arms A and A are connected together by means of acable or cord C which is looped over the pulleys or rollers R, R andpasses below them so that the Spring continuously tends to move therollers M and M toward each other. Such movement is opposed by a load Lacting downwardly at the midpoint of the cable C, the net result beingthat the rollers can be maintained spaced apart any desired distancewithout increasing the load L. It will be obvious from this illustrationthat the constant tension spring S may be used in any environment whereit is desired to maintain a constant tension on two elements even thoughthe distance between the parts is required to be varied from time totime.

should the springs S and S shown in FIGS. 3 and 6, respectively, be usedin their coiled condition, the moment arm of successive convolutionswill vary, so that the force required to unwind the springs willincrease as the springs are unwound and their moment arms becomeshorter. Compensation in the Way of a correction factor may be made formoment arm variations and true constant tension characteristics providedby varying the bending radius the required amount during fabrication.Alter natively, spring material of tapered width and/or thickness may beemployed so the moment arm times the force required to unwind anyincrement of the spring equals a constant.

Compensation for variation in the length of the moment arm of the forcerequired to straighten or tending to rewind the spirally coiled springcan also be had by perforating the spring matreial in such a way as torender the outer end of the spring less resilient than the inner end.Thus, as shown in FIG. 10, the partially uncoiled spring 8" has a seriesof perforations 60 therein. These perforations are spaced apartgradually decreasing distances from the outer end of the spring to theinner end of the spring. This latter variation of the spring isdifiicult to practice in many production operations, as is theproduction of tapered springs, and therefore, these modifications arethe least preferred modifications.

It appears that the constant tension characteristics of preferred typesof springs arise largely from the fact that the portion of the springbeing bent by the dies 35 and 36 is not maintained under tension, andthe spring is merely bent, rather than stretched, during its formation.Because of the lack of stretching, which would cause elongation of thespring material during its formation into the spring, there is notendency for the spring to develop weak zones at its center or along itsedges, which would vary the coiling characteristics of the spring.

Assuming that the above-described springs are bent on the same radius ofcurvature, each convolution thereof normally tends to form a circle ofthe same diameter. However, inasmuch as all of the convolutions of thespring cannot occupy the same space, the spring must initially form aspiral with the convolutions in contact and pressing against each other.

Springs of the type produced in accordance with the method and apparatusdescribed above can be duplicated in quantity and with a high degree ofaccuracy in their characteristics. These springs are uniform in theircharacteristics throughout and are especially suitable for use where auniform tension is required from the spring regardless of the amountthat the spring is extended. Thus, when the spirally coiled spring S isdrawn out endwise into helical form, as shown in FIG. 11, and one end ofthe spring, which may be either end, is secured to a rotary shaft orother member 40 mounted in supports 40*, the free end of the spring maybe drawn out to unwind the spring by the application of a uniform forcethereto. The force applied need not exceed that required to start thespring unwinding, to completely unwind the spring. The spring,therefore, acts very much like a counterweight of fixed value in any ofits wound, partially wound or unwound states. Thus, the spring exerts asmuch tendency to wind up or coil at its inner end as it does at itsouter end, and therefore, compensation need not be made for the extentof unwinding of the coil as is common in the conventional spiral coilsprings. The same results are obtainable if the shaft 40 is omitted andthe spring is mounted in such a way as to permit free body rotation ofthe spring as one of its ends is drawn out.

As shown in FIG. 12, a spring S of helical form, like the spring Sdescribed above, may be mounted loosely in a cylindrical receptacle 41having a slit 42 in one wall through which one end 43 of the springextends. When a force of sufficient magnitude is exerted on the end 43of the spring S, the spring will rotate bodily in the receptacle 41permitting the spring to unwind. Upon release of the force, the spring Swill wind itself up in the receptacle either as a helix or as a group ofconvolutions of equal radius. These convolutions do not necessarilyassume a helical shape and advantage can be taken of this fact to permita very long spring to be mounted in a relatively small space, as shownin FIG.

13. For example, a long slender spring S bent on a uniform radius ofcurvature will have constant tension characteristics if permitted tocoil loosely or at random into a series of convolutions of generallyball-like shape. If this ball-like mass is mounted for free rotation ina hollow, box-like receptacle 44, the spring S may be drawn out througha slot 45 in the receptacle, thereby uncoiling the spring. Release ofthe withdrawn end of the spring will permit it to coil up again into theloose ball-like shape.

While the springs of uniform radius of curvature cannot provide trulyconstant tension characteristics when used as spirally coiled springs,it is possible to modify the characteristics of such spirally coiledsprings to provide the desired constant tension characteristics whenmounted in the manner described above, that is, for free rotation of thespring as a whole. This may be accomplished, as stated, by using taperedstock (width and/or 7 end is bent on the longest radius.

thickness) which, when bent on a constant radius, will have the largersection at the outer end of the coil. The larger sectional area and theconsequent greater resistance to straightening offsets or compensatesfor the longer moment arms through which the applied force acts tostraighten and unwind the spring. It also compensates for the partialstraightening of the spring due to the inability of all of theconvolutions to occupy the same space.

Generally, the same effect may be produced by bending the spring on auniformly varying radius so that the outer end is bent on the shortestradius and the inner This effect can be obtained with my above-describedapparatus by careful manual adjustment of the die elements 22-23 and 35-36, while the spring is being formed, but it is preferable to provide amodified automatic apparatus which will constantly vary the gap betweenthe upper and lower die elements during a forming operation.

A typical apparatus for this purpose is shown in FIG. 14. This apparatusincludes the same general arrangement of die or forming elements 50 and51 as those shown in FIGS. 1 and 4. Instead of employing the clampingbolts and nuts shown in these figures, the modified device is providedwith guide rods 52 and 53 which carry springs 54 and 55. These springsnormally urge the forming members 50 and 51 apart.

A cam 56 is provided with a peripheral portion 57 which uniformlydecreases in radius in a counterclockwise direction from a point 58 to apoint 59 and has a depression 6 between said points. The cam 56 isengaged with a roller 61 carried by a pin 62 mounted in lugs 63 formedon the die member 51. The cam portion 57 is designed so that itgradually moves the die member 51 toward the die member 50 as the cam isrotated. This results in bending successive increments of the springmaterial 64 on a progressively decreasing radius of curvature, so thatthe inner end of the spring thus formed has a greater radius ofcurvature than its outer end and the force required to straighten anyincrement of the spring is the same for all increments, regardless ofchanges in the physical length of the moment arm. When the depression 60is engaged with the roller 61, the die members 50, 51 are permitted tomove apart their maximum distance under the action of the springs 54,55. Reversing the cam, or reversing its direction of rotation, willresult in a coil spring having its outer end portion bent upon a greaterradius of ourvature than its inner end and such spring may be useful forcertain purposes.

The cam 56 may be mounted on a shaft 65, which is supported in bearings66 and 67 and rotated by means of reduction gearing including a gear 68driven at a desired speed in timed relation to the rate of movement ofthe spring material 64 between the dies 50 and 51. The spring material64 can be fed by feed rolls such as the feed rolls 37 and 38 shown inFIG. 4, or pulled by a rod 15 and cylinder 12 such as shown in FIG. 1.

By suitably shaping the cam 56, the spring can be provided, during itsformation, with a uniformly varying curvature, or with a variable orirregular curvature, depending upon requirements. If the drive to thegear 68 is interrupted, the cam 56 can then be manually adjusted to afixed position to maintain the die member 51 in fixed relation to thedie member 50 to form a spring having any desired constant radius ofcurvature.

Adjustment of the member 51 may also be used to compensate forvariations in the thickness of the material being formed into a spring.For example, strip or wire stock may vary in thickness due to errors informing it, so that even a constant radius spring formed from such stockmay actually vary somewhat in its spring characteristics. This variationcan be overcome by determining the variations in thickness and formingthe spring on a correspondingly varying radius of curvature.

FIG. 15 illustrates a constant tension spring embodying the principlesof the present invention, associated with support means for enabling thesame to function as a counterbalance, for example, for a window sash(not shown). Here, the spring S is wound upon the outer periphery of adrum 70 rotatably mounted upon a pin 71 carried by a bracket 72. Thebracket 72 comprises a base portion 73- and flanges 74 and 75 extendingupwardly from the longitudinal edges thereof. The pin 71 is mounted inthe flanges 74 and 75 and serves as a shaft supporting the drum 70 forfree rotation relative thereto.

The radius of the drum 70 is preferably greater than the radius uponwhich the spring has been bent so that the inner convolutions 76 of thespring, in tending to assume its normal diameter, tightly grip the outerperiphery of the drum. The end 77 of the innermost convolution 76 neednot be interengaged with or fastened to the drum 70 in any manner. Thefree end 78 of 19 the spring extends through an opening 79 formed in thebracket base 73 and said lower end may be perforated or suitably shapedfor attachment to a window sash (not shown).

Inasmuch as the resistance offered to unwinding of the spring is notcumulative, the force required to unwind or straighten any givenincrement of the spring S is the same for all other increments of thespring. Variations in the length of the moment arm for successiveconvolutions of the spring, as the spring is being unwound, can becompensated for by employing a spring which has its successiveincrements bent upon a variable radius.

In the case of a window counterbalance, the spring selected will be suchthat it will unwind when a pulling force of only a few ounces is appliedso that very little physical effort is required to unwind the spring toeffect lowering of the sash. On the other hand, the spring inherentlyrewinds itself as the sash is raised and, in this way, substantiallycounterbalances the weight of the sash so that only a very smallphysical force again need be applied to raise the sash.

FIG. 16 illustrates a modified form of cam 56* which may be substitutedin the apparatus shown in FIG. 14 for the cam 56. This cam includes aperipheral portion 80 defined by an are a of constant curvature andanother portion 81 defined by an arc b of constant curvature, but lessthan that of the portion 80. A portion 82 defined by an are c ofuniformly varying curvature is disposed between the portions 88 and 81.The remainder of the cam 56 is defined by a portion including a pocketor depressed region 84 adapted to cooperate with the roller 61 upon thehold-down or die member 51 to permit maximum separation of the diemembers 50 and 51.

It will be apparent that when the cam 56 is mounted upon the shaft 65and rotated in the direction indicated by the arrow, and the portion 80is engaged with the roller 61, the die member 51 will be maintained infixed spaced relation to the die member 50 so that the spring materialthen passing between the dies will be bent upon a constant radius. Whenthe portion 82 of the cam is engaged with the roller, the die member 51is permitted to gradually slide upon the rods 52 and 53 in a directionaway from the die member 51 to progressively increase the width of thegap between the die members 50 and 51 and thereby cause the portion ofthe spring material then passing between said die members to be bentupon a varying, progressively increasing radius. As the cam 56 continuesto rotate, the portion 81 will contact the roller 61 and again maintainthe die members 50 and 51 in fixed spaced relation, but with the gapwider than when the cam portion 80 was engaged with said roller. Thespring material then being passed between the die members 50 and 51 willbe bent upon a constant radius, greater than the radius R. A spring thusformed is diagrammatically illustrated in FIG. 17 and generallyidentified by the letter S It will be noted from this figure that theinner convolutions 85 of the spring are formed upon a constant radius R,whereas the outer convolutions 86 of said spring are formed upon arelatively greater constant radius indicated by the letter R. Theintermediate convolutions 87 of the spring 84 are bent upon theconstantly varying radius Rv, which progressively increases from theradius R to the radius R. Reverse mounting or reverse driving of the cam56 will result in a spring having its convolutions bent in the reverserelation from that described above.

It will be apparent that by varying the contour of the earns 56 and 56 aspring having any desired tension characteristics, constant orotherwise, can be automatically formed, and such desired characteristicscan be accurately reproduced in the successive springs formed by themachine with any given cam design.

FIGS. 18 to 23 illustrate still another form of machine forautomatically coiling springs which embodies the principles of thepresent invention.

Referring now more particularly to FIG. 18, the machine comprises a bedplate 100 supported upon frame members 101 at opposite edges, only oneof said frame members being shown in the drawings. A bracket 102 isadjustably secured to the underside of the bed plate by machine bolts103 and serves as a journal for a shaft 104 having a feed roll 105secured thereto. A similar feed roll 106 is secured to a shaft 107rotatably mounted in a bracket 108, which is also adjustably secured tothe bed plate 100 by bolts 109. The brackets 102 and 108 carrying thefeed rolls 105 and 106 are so adjusted that said feed rolls engage thespring material 109 with sufficient pressure to force the same through apair of bending dies 110 and 111, which have confronting faces similarto those of the dies 22 and 23.

A guide 112 is interposed between the discharge side of the feed rolls105 and 106 and the entrance gap G of the die blocks 110 and 111. Theguide 112 comprises a bracket 113 secured to the underside of the bedplate 100 by bolts 114. The bracket 113 is provided with a channel 115(FIG. 19) through which the spring material 109 passes and is guided sothat it travels upwardly in a path perpendicular to the forming faces ofthe die blocks 110 and 111. In other words, the gap between the dieblocks 110 and 111 is L-shaped, with one leg of the L in a straight linewith the guide channel 115. The spring material 109 is retained in thechannel 115 by a plate 116 secured to the bracket 113 by screws 117.

The die member 110 is secured to the bed plate 100 by a plurality of capscrews 118. The cooperating die block or hold-down member 111 is securedto an inclined platform 119 by a plurality of cap screws 120.

The platform 119 is supported at an angle of about 45 to the horizontalby a pair of guide rods 121 extending in a plane common to the radius ofthe convex corner of the die block 110. The lower end of each guide rod121 is received in a bracket 122 adjacent one end of the die block 110.Each of the brackets 122 is. secured to the bed plate 100 by cap screws123. A pin 124 retains the lower end of the guide rods 121 in thebrackets 122 and holds said rods against rotation. The upper end of eachguide rod 121 is received in and supported by a bracket 125 secured tothe bed plate by cap screws 126.

The guide rods 121 extend through an opening 127 extending transverselythrough the platform 119 and the intermediate portion of each guide rod121 is provided with threads 128. The platform 119 is provided withlongitudinal slots 129 each of which intersects one of the openings 127.An internally threaded travelling nut 130 is disposed in each of theslots and is engaged with the threads 128. Each of the nuts 130 iskeyed, as best shown in FIG. 21, to a worm wheel 131, which is alsodisposed in each of the slots 129.

A reversible, constant speed electric motor 132 is mounted upon theplatform 119 by bolts 133, and has a shaft 134 projecting from each endthereof. A worm 135 is secured to each end of the shaft 134 and mesheswith one of the worm wheels 131. A conventional, electrically operatedbrake 136 is suitably mounted upon the platform 119 and is adapted tocooperate with the shaft 134 to prevent overrunning thereof at such timewhen the current to the motor 132 is cut off, all as will be explainedmore fully hereinafter.

It will be apparent from the foregoing that when the motor 132 isrotating in one direction, say forward, the worms 135 will cause theworm wheels 131 to turn and thus rotate the travelling nuts 130 to causethe platform 119 to travel along the guide rods 121 in a directiontoward the die block 110, thereby moving the hold-down member 111 towardsaid die block and decreasing the width of the gap therebetween. On theother hand, when the motor 132 is rotated in the opposite, or reverse,direction the worms 135 will rotate the worm wheels 131 in the oppositedirection and cause the platform 119 to travel along the guide rods 121in a direction away from the die block 110, thereby increasing the widthof the gap between said die block and the hold-down member 111. Thepitch of the threads 128 and the drive ratio of the worm and the wormwheel 131 are designed so as to move the hold-down member 111 relativeto the die block 110 to bend the spring material 109 upon any constantor varying radius desired, so that the finished spring will have anytension characteristics desired.

The travel of the platform 119 carrying the hold-down member 111 may becontrolled in any number of different ways. However, for illustrativepurposes, one form of operative automatic, electric control means isillustrated and described herein. The control means is convenientlymounted upon a stationary platform 140 suitably secured to the machinelegs 101. Bracket means 141 is mounted upon the platform 140 androtatably supports a shaft 142. A control cam 143 is secured to theshaft 142 so that it is driven thereby. A roller 144 engages theperiphery of the cam 143 and is rotatably mounted upon a pin 145 mountedin an arm 146. The arm 146 has one end thereof pivotally supported by apin 148 mounted in one of the legs 101. A spring 149, which may be aconstant tension spring embodying the principles of the presentinvention, has the coiled portion thereof engaged with an off- Set inthe arm 146 and one end thereof is secured at 150 to a rod 151 mountedon the platform 140. The spring 149 thus constantly urges the roller 144into contact with the periphery of the cam 143 under a constantpressure.

An upright rod 152 has its lower end threaded and mounted in a threadedopening 153 formed in the platform 140. A block or frame member 154,preferably formed of electrical insulating material, is adjustablysecured to the rod 152 by a set screw 155, the portion of the rod 152engaged by the frame 154 being rectangular in cross-section so that saidframe cannot turn relative to said rod. The frame 154 includes an upperarm 156 having a conventional, normally open Micro switch 157 mountedthereon, and a lower arm 158 having a similar switch 159 mountedthereon.

The arm 146 carries a flat spring member 160 provided with an insulateddouble contact 161. The contact 161 is adapted to engage with a contact162 on a C- shaped conductor mounted on the frame 154, or with a similarcontact 163 on said conductor, depending upon which portion of the cam143 is engaged with the roller 144. The contact 161 has an intermediateposition in which it is engaged with neither contact 162 nor 163 and atsuch time the circuit to the motor 132 is interrupted, as will appearmore fully hereinafter. However, the spring strip 160 is arranged sothat it is adapted to engage and actuate the sensitive operating pin 164of the Micro switch 157 shortly after the contact 161 has engaged thecontact 162, and to likewise engage and actuate the sensitive pin 165 ofthe Micro switch 159 after the contact 161 has engaged the contact 163.The reason for this is that the contacts 162 and 163 are associated withrelays, which will be described later, adapted to simultaneously releasethe brake 136 and complete the circuit to the motor 132, andalternatively, to simultaneously apply said brake and interrupt thecircuit to said motor, all as will be described more 'fully later.

The cam 143 (FIG. 23) includes a portion which is of greater radius thana portion 171 thereof. The cam 143 also includes portions 172 and 173defined by a radius less than that of the portion 170 but greater thanthat of the portion 171. The roller 144 is shown engaged with theportion 172 at which time the contact 161 is in its intermediateposition and is not engaged with either the contact 162 or the contact163. When the portion 170 of the cam is engaged with the roller 144, thecontact 161 will be raised into engagement with the contact 162, andwhen the cam portion 171 is engaged with the 13 roller 144, the spring149 will cause the arm 146 to move in a counterclockwise direction aboutits pivot 148 and thus engage the contact 161 with the contact 163.

The electrical control means for the machine further includes a normallyclosed relay 175 (FIG. 23) and a normally open relay 176, both of whichmay obviously be mounted upon the platform 140. The relays 175 and 176are operated by six volt direct current produced by a transformer 177,which may also be mounted upon the platform 140.

FIG. 23 illustrates the manner in which the motor 132, brake 136, Microswitches 157 and [159, the relays 175 and 176, transformer 177, etc.,are interconnected in a circuit for automatically controlling themachine. Thus, electric current is supplied to the machine through 110volt A.C. main conductors 180 and 181. Leads 182 and 103 connect theconductors 180 and 181, respectively, with the primary coil of thetransformer 177. A wire 164 connects one side of the secondary coil ofthe transformer with the contact 161. The other side of the secondarycoil of the transformer 177 is connected by a Wire 1185 to the relay 175whose contacts 186 and 187 are normally closed. Another Wire 160 extendsfrom the relay 175 to the relay 176 whose contacts 189 and 190 arenormally open. Another wire 191 extends from the relay 176 to thecontacts 162 and 163. Thus, the relays 175 and 176 are connected inseries.

The Micro switch 157 is diagrammatically illustrated as comprisingcontacts 193 and 194, and the Micro switch 159 is similarly illustratedas comprising contacts 195 and 196.

One terminal 197 of the brake 136- is connected with the conductor 100and the other terminal 198 is connected by a wire 199 with the contact187 of the normally-closed relay 175. The other contact 186 of the relay175 is connected by a wire 200 with the other conductor 181. With thecontact 161 intermediate the contacts 162 and 163, as shown, the circuitto the brake 136 is completed through the conductor 180, wire 199,contacts 186 and 187 of the relay 175, wire 200 and conductor 181, sothat the brake is applied and holds the motor shaft 134 againstrotation. This relationship corresponds to the position of the roller144 when engaged with either of the cam portions 172 and 173 of thecontrol cam 143.

One terminal 201 of the motor 132 is connected by a wire 202 with thecontact 139 of the normally-open relay 176, and the other contact 190 ofsaid relay is connected by a wire 203 with the conductor 180. One of thecontacts 193 of the switch 157 is connected by a lead 204 with the wire202 and the other contact 194 of said switch is connected by a wire 205with a second terminal 206 of the motor 132. The contact 195 of theMicro switch 159 is connected by a lead 207 with the wire 205, and theother contact 196 of said switch is. connected by a lead 208 with theconductor 181, said conductor being connected to a third terminal 209 ofsaid motor.

Assuming that the cam 143 has rotated clockwise to a position such thatthe cam portion 170 engages the roller 144, the contact 161 will thenengage the contact 162, and the circuit to the relays 175 and 176 willbe completed so that both relays are energized. The circuit is completedfrom one side of the secondary winding of the transformer 177 throughthe wire 105, the coil of relay 175, wire 188, the coil of relay 176,through the wire 191, contacts 162 and 161, and back through wire 184 tothe other side of said secondary winding. Energization of the relay 175opens the contacts 186 and 187 thereof, thereby interrupting the circuitto the brake 136 and releasing the motor shaft 134 for rotation. Thesimultaneous energization of the relay 176 causes the contacts 189 and190 thereof to engage, and the actuation of the pin 164 of the Microswitch 157 by the spring strip 160 causes the contacts 193 and 194 ofsaid switch to engage and thereby complete the circuit to the motor 132to drive the same in a forward direction, -i.e., to move the die memberto slowly decrease the width of the gap G, FIG. 18. The circuit to themotor 132' is then completed through the main conductor 180, relaycontacts 189 and 190, and wire 202 and 20 1-, Micro switch contacts 193and 194, wire 205 to one terminal 206 of the motor 132, and from motorterminal 209 to the other main conductor 181. With the cam 1143 designedas illustrated, the motor 132 will continue to rotate in a forwarddirection during almost a half revolution of the earn 143 indicated bythe angle P. During this period, the platform 119 will be very slowlymoved in a direction toward the die block 110, carrying the hold-downmember 111 with it, so that the gap G between the hold-down member 111and the die block 110 very slowly decreases with the result that theradius of curvature upon which the spring material is bent will verygradually decrease as the strip of spring material 109 is passed betweensaid die block and hold-down member. The bending of the spring material109 will have been completed by the time that the portion 173 of the cam143 is engaged with the roller 144. At such time, the contact 161 willbe returned to its intermediate position and the circuit will then be inthe condition initially described, namely, with the brake 136 appliedand the circuit to the motor 132 interrupted. Continued rotation of thecam 143 will then place the cam portion 171 in contact with the roller144, thereby enabling the spring 149 to actuate the arm 146 to engagethe contact 161 with the contact 163, whereupon the relays and 176 areagain energized as previously described, to effect release of the brake136 and complete the circuit to the motor 180. The Micro switch 159 isactuated as an incident to the engagement of the contact 161 with thecontact 163 through the actuation of the switch pin 165 by the springarm 160 so that the contacts 195 and 196 of said switch are closed tothereby complete the circuit to the motor 132. The circuit to the motor132 is then completed through the main conductor 180, relay contacts 189and 190 and wire 202 to motor terminal 201 and from motor terminal 206through wires 205, 207, Micro switch contacts and 196, Wire 208 andthrough the other conductor 181. The motor will then be driven in areverse direction to move the hold-down member 111 back to its initialposition corresponding to the beg-inning of a bending operation to beperformed upon a length of spring material. The cam portion 171 isdefined by an are q which is equal to the are p, so that the forward andreverse time periods of operation of the motor 132 are identical.

Any conventional cut-off means may be provided to sever the formedspring after the bending operation has been completed. FIG. 18illustrates in dot-and-dash line an anvil 210 which may be mounted inany suitable manner upon the bed 100, and a cooperating cut-off member211 which may be reciprocated relative to the anvil 210 by anyconventional means. The cult-oil member 211, of course, is to beautomatically operated in proper timed relation with the movement ofother parts of the machine.

In one mode of operation of the machine, the drive rolls 105 and 106 arerotated only during the portion of the cycle that the motor 132 is beingoperated in the forward direction, i.e., advancing the hold-down member111 toward the die block 110 while the spring material is being bent.This will produce a constant tension spring in which the inner end ofthe spring is bent upon a greater radius of curvature than the outer endand in which the curvature of the bent portion of the springprogressively decreases from end to end. The operation of the feed rolls105 and 106 is interrupted after the spring has been completely formed,and during the time that the motor is being driven in a reversedirection to return the holddown member 111 to its retracted positionpreparatory to the bending of the spring material 109 to form anotherspring.

FIG. 22 schematically illustrates drive means for the feed rolls 105 and106 and the control cam 143, whereby the foregoing may be effected.Thus, a gear 215 is secured to the shaft 107 carrying the feed roll 106,and a gear 216 meshing with the gear 215 is secured to the shaft 104carrying the other feed roll 105. A large gear 217 is mounted upon amain drive shaft 218, and is provided with teeth 219 extending onlythrough half of its circumference, whereby to effect intermittentdriving of the gear 216. The shaft 213 is journaled in a bracket 218'secured to the bed 100 and may be driven by any suitable means (notshown). A stop segment 220 is secured to the gear 216 in cooperatingrelation with a blocker segment 221 carried by the gear 219 at theportion of the periphery thereof which is devoid of the driving teeth219. A gear 222 is secured to the drive shaft 213 and meshes with a gear223 mounted upon the cam shaft 142. Thus, the cam shaft 142 iscontinuously rotated; whereas, the gears 216 and215, which drive thefeed rolls 105 and 106, are rotated only at such time as the portion ofthe cam 170 is engaged with the roller 144 and the hold-down member 111is being very slowly advanced. The drive arrangement is such that thedriving of the gear 216 is discontinued at the time that the platform119 reaches the desired advanced position. The blocker segment 221 thencooperates with the stop 220 to hold the gear 216 stationary while thecam portion 171 is engaged with the roller 144 to effect driving of themotor 132 in a reverse direction to retract the platform 119 and thehold-down member 111 carried thereby to its starting position. Thus, thefeed rolls 105 and 106 are idle while the hold-down member 111 is beingretracted. The cut-off member 211 may be actuated at any time during theinterval that the drive of the feed rolls 105 and 106 is interrupted.

While spring material 109 is being fed by the feed rolls 105 and 106,the guide means 112 will position said spring material for movement in apath substantially perpendicular to the working surfaces of the dieblocks 110 and 111 so that as the spring material is bent and windsitself up into a coil, the several convolutions of the coil will bedisposed in a substantially common radial plane.

While only one set of feed rolls and one guide has been illustrated inthe machine disclosed in FIGS. 18 and 20, it will be apparent that anynumber of each may be employed, so that a plurality of springs may besimultaneously bent, and thus enable the same to be economically andquickly mass-produced in large numbers.

FIG. 24 illustrates a modified form of cam 230 that may be mounted uponthe shaft 142 in lieu of the cam- 143 to cause the die block 111 to beretracted instead of advanced at the beginning of a bending cycle toproduce a spring having different characteristics from that formed underthe control of the cam 143. The cam 230 includes two arcuate portions231 and 232 corresponding to the portion 170 of the cam 143, but which,when engaged with the roller 144, actuate the contact 161 to effectoperation of the motor 132 in a reverse direction at that time toretract the die member 111 in two stages from its fully advancedposition. The cam 230 also includes arcuate portions 233, 234, 235corresponding to portions 172 and 173, which respectively interrupt thecircuit to the motor 132 and apply the brake 136 whenever these portionsare engaged with the roller 144. A cam portion 236 disposed between thecam portions 233 and 235 corresponds to the portion 171 of cam 143which, when engaged with the roller 144, effects driving of the motor132 in a forward direction, to thereby advance and return the platform119 and the die block 111 toward their initial starting position in onestage.

The cam portions 231 and 232, respectively, extend through an angle of55 so that the motor 132 is intermittently driven in a reverse directionthrough a total angle of 110" of revolution of the cam 230 to graduallyretract the die block 111. The cam portion 231 is effective for a periodof time corresponding to an angular movement of 55 of the cam 230, theoperation of the motor 132 being interrupted when the portion 234 of thecam engages with the roller 144, the reverse driving of the motor 132being continued when the portion 232 of the cam 230 engages with theroller 144 for a period of time corresponding to another 55 of angularmovement of the cam 230. The driving of the motor 132 is againinterrupted when the cam portion 235 engages the roller 144, and itsdirection of rotation is subsequently changed and it rotates in aforward direction to return the die block 111 toward the die block 110when the cam portion 236 is engaged with the roller 144. The forwarddrive continues for a period of time corresponding to a total angularrotation of 110 of the cam 230, so that the die block 111 is returned toexactly the same position it occupied close to the die block 110 at thebeginning of the spring-forming cycle. The driving of the motor, ofcourse, is again interrupted at the end of the cycle when the camportion 233 is engaged with the roller 144.

It will be understood that the feed rolls 104 and 105 feed springmaterial to the die blocks and 111 while the cam portions 231, 235 and232 of cam 230 are actively engaged with roller 144, as is done whilethe cam portion of cam 143 is active, and that the feed is interruptedbefore cam portion 236 becomes active.

FIG. 25 schematically illustrates a spring S which can be formed underthe control of the cam- 230, it being understood that the spacing of theconvolutions of said spring has been exaggerated for illustrativepurposes. It will be noted that the inner convolutions 240 of the springare bent upon a uniformly varying but increasing radius, correspondingto the retraction of the die block 111 during the time that the camportion 231 is engaged with the roller 144. The intermediateconvolutions 241 of the spring are bent upon a constant radius,corresponding to the interval that the portion 234 of the cam is engagedwith the roller 144, and the circuit to the motor 132 is interrupted andthe die block 111 is held stationary. The outer convolutions 242 of thespring are bent upon a uniformly varying but increasing radius,corresponding to the period during which the cam portion 232 is engagedwith the roller 144 and the motor 132 is interrupted and the die block111 is held stationary. The outer convolutions 242 of the spring arebent upon a uniformly varying but increasing radius, corresponding tothe period during which the cam portion 232 is engaged with the roller144 and the motor 132 is slowly moving the die block 111 away from thedie block 110. The varying radius of the outer convolutions 241 isgreater than the varying radius of the inner convolutions 240.

It will be understood that other cams, in addition to the cam 230, canbe substituted for the cam 143 and properly timed with the machine cycleto provide coil springs having one or more portions thereof bent upondifferent constant radii, and/or one or more portions thereof bent upondifferent varying radii of curvature.

It will also be understood that the automatic control of the motor 132can be rendered ineffective at any time by manually opening a mainswitch M, FIG. 23. Thus, if it is desired to form a number of springs bybending the spring material 109 upon any desired constant radius for thefull length of the springs, then the circuit to the motor 132 can bemanually interrupted by opening switch M when the hold-down member 111is spaced the correct distance from the die member 110 to effect bendingof said spring material upon such constant radius of curvature.

It will be apparent from the preceding description that the apparatusand the methods of forming the strips, as well as the characteristics ofthe resulting springs, may be modified considerably without departingfrom the invention, Therefore, the forms of the invention de- 17 scribedherein should be considered as illustrative and not as limiting exceptas required by the scope of the following claims.

I claim:

1. The method of making a non-cumulative force spring which comprisessuccessively sharply bending to a predetermined radius each increment ofan elongated piece of material having spring characteristics to effectan initial set of the material so that it tends to coil tightly onitself in one direction, reverse bending the material to set eachincrement of the material so that it still tends to coil tightly onitself in the same direction but on a radius larger than the radius ofinitial set and allowing the thusly treated material to wind itself upinto a plurality of convolutions with the successive convolutions incontact, to thereby provide a tightly wound non-cumulative force spring.

2. The method of making a non-cumulative force spring which comprisessuccessively sharply bending to a predetermined radius each increment ofa length of an elongated piece of material having spring characteristicsto effect an initial set of each increment of said length so that thesaid length tends to coil tightly on itself in one direction, partiallystraightening the length of material to set each increment of the lengthto a radius larger than the radius of initial set, the said length stilltending to coil tightly on itself in the same direction and allowing thethusly treated material to wind itself up into a plurality ofconvolutions with the successive convolutions in contact to therebyprovide a tightly wound non-cumula-tive force spring.

3. The method of making a non-cumulative force spring in a continuousoperation which comprises first bending sharply successive increments ofan elongated piece of metal having spring characteristics to set themetal so that it tends to coil tightly on itself in one direction,restraining the increments from coiling and reverse bending eachincrement of the metal after the first bending to set each increment ofthe metal so that it still tends to coil tightly on itself in the samedirection but on a radius larger than the radius of initial set andallowing the thusly treated metal to wind itself up into a plurality ofconvolutions with the successive convointions in contact, to therebyprovide a tightly wound non-cumulative force spring.

4. The method of making a non-cumulative force spring in a continuousoperation which comprises pulling an elongated piece of metal havingspring characteristics around a forming member to bend sharplysuccessive increments of said metal to set the metal so that it tends tocoil tightly on itself in one direction, restraining the increments fromcoiling and reverse bending each increment of the metal to set eachincrement of the metal so that it still tends to coil tightly on itselfin the same direction but on a radius larger than the radius of initialset and allowing the thusly treated metal to wind itself up into aplurality of convolutions with the successive convolutions in contact,to thereby provide a tightly wound non-cumulative force spring.

References Qited in the file of this patent OTHER REFERENCES 1,787,936Forest Jan. 6, 1931 1,837,209 Dallas Dec. 22, 1931 1,935,501 Hudson Dec.25, 1934 2,038,305 Mikaelson et al. Apr. 21, 1936 2,071,137 Neidt Feb.16, 1937 2,179,011 Hudson Nov, 7, 1939 2,192,101 Peskin Feb. 27, 19402,246,239 Brand June 17, 1941 2,395,651 Anderson Feb. 26, 1946 2,609,191Foster Sept. 2, 1952 2,609,192, Lermont Sept. 2, 1952 2,609,193 FosterSept. 2, 1952 2,647,743 Cook Aug. 4, 1953

